Does a regulator make a dirt bike not crank?

No--a voltage regulator would prevent a battery charging. Your dirtbike most likely has a magneto, feeding a coil or spark exciter. Test park by pulling spark plug, reinserting plug into plug wire, grounding electrode on motor head, and turning over engine. You should get a "blue," audible spark. A weak yellow spark indicates a bad coil; no spark is usually a failed magneto--quite often the shear-pin has been sheared, and the magneto is now out of timing. All of these fixes are pretty easy, a new coil being the most expensive.